Weight & mass converters
Mass measures the amount of matter. US customary pounds and international kilograms are common. Choose an exact direction below, or open the universal converter for all compatible units.
Example weight & mass conversions
Start with a calculated reference value, then open the tool to enter your own measurement. Results marked ≈ are rounded for display.
- Pounds to Kilograms1 lb = 0.45359237 kg
- Ounces to Grams1 oz = 28.349523125 g
Understanding weight & mass
Mass is not force
Pounds (lb) and kilograms (kg) measure mass. Pound-force (lbf), by contrast, measures force; a mass-to-force calculation requires an acceleration such as gravity. Never interchange lb and lbf labels.
How to verify a conversion
One international avoirdupois pound is defined as exactly 0.45359237 kilogram. Smaller displayed decimal counts are rounding choices, not new physical definitions.
Source definitions: NIST Guide to the SI. See our conversion methodology for calculation and rounding details.
Accurate calculations, no guesswork
Every converter uses consistent unit definitions and returns an interactive result you can verify. For multiple measurements, use the batch converter.
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